Engineering disasters: Chernobyl

In April 1986, people’s worst nightmares about nuclear energy came true. How do we make sure the same thing doesn’t happen again?

In the early hours of 26th April, 1986, Chernobyl nuclear reactor exploded. Initially citizens in the nearby city of Pripyat were told that there was a problem, but that it was being dealt with. Twenty-four hours later, the whole city was evacuated, as the radiation emitted by Chernobyl reactor had started to spread.

The incident was the worst nuclear power plant accident in history. Over 300,000 people had to be relocated, and over 50 people died as a direct cause of the accident. The area around Chernobyl is still contaminated.

Why did it happen?

Engineers began an experiment to see whether the cooling pump system, which regulates the temperature inside the reactor, could function on low power in case of emergency.

During the experiment the reactor began to overheat and the engineers decided to shut it down. However, the power inside the reactor had become so high that when the emergency shutdown was initiated, fuel pellets inside the core of the reactor began to explode.

This caused two much larger explosions which destroyed the reactor and started fires at the plant, which burned for nine days.

How would engineers fix it?

At the time, damage from Chernobyl radiation was minimised by enclosing the destroyed reactor in a concrete ‘sarcophagus.’ This is not a means of fixing the reactor, but simply a way of making sure that no more radioactive material gets released into the atmosphere.

The sarcophagus around Chernobyl is beginning to deteriorate, and engineers are working on a new solution which will be installed over the old sarcophagus in 2011.